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Program to Find Roots of a Quadratic Equation
#include <math.h>
#include <stdio.h>
int main() {
double a, b, c, discriminant, root1, root2, realPart,imagPart;
printf("Enter coefficients a, b and c: ");
scanf("%lf %lf %lf", &a,&b, &c);
discriminant = b * b - 4 * a * c;
// condition for real and different roots
if (discriminant > 0) {
root1 = (-b + sqrt(discriminant)) / (2 * a);
root2 = (-b - sqrt(discriminant)) / (2 * a);
printf("root1 = %.2lf and root2 = %.2lf", root1, root2);
}
// condition for real and equal roots
else if (discriminant == 0) {
root1 = root2 = -b / (2 * a);
printf("root1 = root2 = %.2lf;", root1);
}
// if roots are not real
else {
realPart = -b / (2 * a);
imagPart = sqrt(-discriminant) / (2 * a);
printf("root1 = %.2lf+%.2lfi and root2 = %.2f-%.2fi", realPart,imagPart, realPart,imagPart);
}

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return 0;
}
Fibonacci Series up to n terms
#include <stdio.h>
int main() {
int i, n, t1 = 0, t2 = 1, nextTerm;
printf("Enter the number of terms: ");
scanf("%d", &n);
printf("Fibonacci Series: ");
for (i = 1; i <= n; ++i) {
printf("%d, ", t1);
nextTerm = t1 + t2;
t1 = t2;
t2 = nextTerm;
}
return 0;
}
Armstrong Numbers Between Two Integers
#include <math.h>
#include <stdio.h>
int main() {
int low, high, i, temp1, temp2, rem, n = 0;
float result = 0.0;
printf("Enter two numbers(intervals): ");
scanf("%d %d", &low, &high);
printf("Armstrong numbers between %d and %d are: ", low, high);
for (i = low + 1; i < high; ++i) {
temp2 = i;
temp1 = i;
// number of digits calculation
while (temp1 != 0) {
temp1 /= 10;
++n;
}
// result contains sum of nth power of its digits
while (temp2 != 0) {
rem = temp2 % 10;
result += pow(rem, n);
temp2 /= 10;
}
// check if i is equal to the sum of nth power of its digits
if ((int)result == i) {

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printf("%d ", i);
}
// resetting the values
n = 0;
result = 0;
}
return 0;
}
Program to Check Prime Number
#include <stdio.h>
int main() {
int n, i, flag = 0;
printf("Enter a positive integer: ");
scanf("%d", &n);
for (i = 2; i <= n / 2; ++i) {
// condition for non-prime
if (n % i == 0) {
flag = 1;
break;
}
}
if (n == 1) {
printf("1 is neither prime nor composite.");
}
else {
if (flag == 0)
printf("%d is a prime number.", n);
else
printf("%d is not a prime number.", n);
}
return 0;
}
Display Prime Numbers Between two Intervals
#include <stdio.h>
int main() {
int low, high, i, flag;
printf("Enter two numbers(intervals): ");
scanf("%d %d", &low, &high);
printf("Prime numbers between %d and %d are: ", low, high);
while (low < high) {
flag = 0;

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// if low is a non-prime number, flag will be 1
for (i = 2; i <= low / 2; ++i) {
if (low % i == 0) {
flag = 1;
break;
}
}
if (flag == 0)
printf("%d ", low);
++low;
}
return 0;
}
Program to convert binary to decimal
#include <math.h>
#include <stdio.h>
int convert(long long n);
int main() {
long long n;
printf("Enter a binary number: ");
scanf("%lld", &n);
printf("%lld in binary = %d in decimal", n, convert(n));
return 0;
}
int convert(long long n) {
int dec = 0, i = 0, rem;
while (n != 0) {
rem = n % 10;
n /= 10;
dec += rem * pow(2, i);
++i;
}
return dec;
}
#include <math.h>
#include <stdio.h>
int convert(long long n);
int main() {
long long n;
printf("Enter a binary number: ");
scanf("%lld", &n);
printf("%lld in binary = %d in decimal", n, convert(n));
return 0;
}
int convert(long long n) {
int dec = 0, i = 0, rem;

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while (n != 0) {
rem = n % 10;
n /= 10;
dec += rem * pow(2, i);
++i;
}
return dec;
}
Output
Enter a binary number: 110110111
110110111 in binary = 439
Program to convert decimal to binary
#include <math.h>
#include <stdio.h>
long long convert(int n);
int main() {
int n;
printf("Enter a decimal number: ");
scanf("%d", &n);
printf("%d in decimal = %lld in binary", n, convert(n));
return 0;
}
long long convert(int n) {
long long bin = 0;
int rem, i = 1, step = 1;
while (n != 0) {
rem = n % 2;
printf("Step %d: %d/2, Remainder = %d, Quotient = %dn", step++, n, rem, n / 2);
n /= 2;
bin += rem * i;
i *= 10;
}
return bin;
}
Output
Enter a decimal number: 19
Step 1: 19/2, Remainder = 1, Quotient = 9
Step 2: 9/2, Remainder = 1, Quotient = 4
Step 3: 4/2, Remainder = 0, Quotient = 2
Step 4: 2/2, Remainder = 0, Quotient = 1
Step 5: 1/2, Remainder = 1, Quotient = 0
19 in decimal = 10011 in binary
For example we want to convert decimal number 525 in the octal.
Step 1: 525 / 8 Remainder : 5 , Quotient : 65
Step 2: 65 / 8 Remainder : 1 , Quotient : 8

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Step 3: 8 / 8 Remainder : 0 , Quotient : 1
Step 4: 1 / 8 Remainder : 1 , Quotient : 0
So equivalent octal number is: 1015
That is (525)10 = (1015)8
Example 1: Program to Convert Decimal to Octal
#include <stdio.h>
#include <math.h>
int convertDecimalToOctal(int decimalNumber);
int main()
{
int decimalNumber;
printf("Enter a decimal number: ");
scanf("%d", &decimalNumber);
printf("%d in decimal = %d in octal", decimalNumber, convertDecimalToOctal(decimalNumber));
return 0;
}
int convertDecimalToOctal(int decimalNumber)
{
int octalNumber = 0, i = 1;
while (decimalNumber != 0)
{
octalNumber += (decimalNumber % 8) * i;
decimalNumber /= 8;
i *= 10;
}
return octalNumber;
}
Output
Enter a decimal number: 78
78 in decimal = 116 in octal
Example 2: Program to Convert Octal to Decimal
#include <stdio.h>
#include <math.h>
long long convertOctalToDecimal(int octalNumber);
int main()
{
int octalNumber;

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printf("Enter an octal number: ");
scanf("%d", &octalNumber);
printf("%d in octal = %lld in decimal", octalNumber, convertOctalToDecimal(octalNumber));
return 0;
}
long long convertOctalToDecimal(int octalNumber)
{
int decimalNumber = 0, i = 0;
while(octalNumber != 0)
{
decimalNumber += (octalNumber%10) * pow(8,i);
++i;
octalNumber/=10;
}
i = 1;
return decimalNumber;
}
Output
Enter an octal number: 116
116 in octal = 78 in decimal
Hexadecimal number system: It is base 16 number system which uses the digits from 0 to 9 and A,
B, C, D, E, F.
Decimal number system:
It is base 10 number system which uses the digits from 0 to 9
Decimal to hexadecimal conversion method:
Following steps describe how to convert decimal to hexadecimal
Step 1: Divide the original decimal number by 16
Step 2: Divide the quotient by 16
Step 3: Repeat the step 2 until we get quotient equal to zero.
Equivalent binary number would be remainders of each step in the reverse order.
Decimal to hexadecimal conversion example:

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For example we want to convert decimal number 900 in the hexadecimal.
Step 1: 900 / 16 Remainder : 4 , Quotient : 56
Step 2: 56 / 16 Remainder : 8 , Quotient : 3
Step 3: 3 / 16 Remainder : 3 , Quotient : 0
So equivalent hexadecimal number is: 384
That is (900)10 = (384)16
C Program
1. #include<stdio.h>
2. int main() {
3. long int decimalNumber,remainder,quotient;
4. int i=1,j,temp;
5. char hexadecimalNumber[100];
6. printf("Enter any decimal number: ");
7. scanf("%ld",&decimalNumber);
8. quotient = decimalNumber;
9. while(quotient!=0) {
10. temp = quotient % 16;
11. //To convert integer into character
12. if( temp < 10)
13. temp =temp + 48; else
14. temp = temp + 55;
15. hexadecimalNumber[i++]= temp;
16. quotient = quotient / 16;
17. }
18. printf("Equivalent hexadecimal value of decimal number %d: ",decimalNumbe
r);
19. for (j = i -1 ;j> 0;j--)
20. printf("%c",hexadecimalNumber[j]);
21. return 0;
22.}
Output
1. Enter any decimal number: 45
2. Equivalent hexadecimal value of decimal number 45: 2D
Program to Check Palindrome
#include <stdio.h>
int main() {

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int n, reversedN = 0, remainder, originalN;
printf("Enter an integer: ");
scanf("%d", &n);
originalN = n;
// reversed integer is stored in reversedN
while (n != 0) {
remainder = n % 10;
reversedN = reversedN * 10 + remainder;
n /= 10;
}
// palindrome if orignalN and reversedN are equal
if (originalN == reversedN)
printf("%d is a palindrome.", originalN);
else
printf("%d is not a palindrome.", originalN);
return 0;
}
Power ofa Number Using the while Loop
#include <stdio.h>
int main() {
int base,exp;
long long result = 1;
printf("Enter a base number: ");
scanf("%d", &base);
printf("Enter an exponent: ");
scanf("%d", &exp);
while (exp != 0) {
result *= base;
--exp;
}
printf("Answer = %lld", result);
return 0;
}
Output
Enter a base number: 3
Enter an exponent: 4
Answer = 81